The appropriate methods of cancer screening and prevention in carriers of breast cancer predisposition gene mutations are unknown. We propose to conduct an observational study of mutation carriers to determine current screening practices. We will also determine the effect of prophylactic oophorectomy on the risk of ovarian/peritoneal cancer. This study will promote a collaborative effector between the Cooperative Family Registry for Breast Cancer Studies and wider research community and will provide subjects and an infrastructure for conductive definitive studies of breast and ovarian cancer screening and prevention.